A rarefied hypersonic flow through a channel containing a wedge is simulated using the combined direct simulation Monte Carlo and monotonic Lagrangian grid methodologies on the massively parallel Connection Machine. Numerical issues related to the effects of resolution in terms of the simulated to actual particle ratio and the use of time averaging to obtain a statistically converged solution are discussed. Because the flow is rarefied, important aerodynamic features are diffuse compared to what is expected in a continuum flow. For example, the reattachment shock behind the trailing edge of the wedge degenerates into a diffuse viscous layer. Other low-density effects include the velocity slip, which peaks near the leading edges where the density is low, and the temperature jump of the gas adjacent to the solid surfaces, which is highest at the entrance of the channel and decreases farther downstream. The calculated skin friction and heat transfer agree well with the Reynolds analogy for boundary-layer flow.